1. Technical Field of the Invention
This invention relates to a plasma display panel, which is favorable as a flat display panel, and a manufacture method thereof, and in particular relates to a plasma display panel and a manufacturing method thereof, with which the productivity is improved by reduction of the number of manufacturing processes.
2. Description of the Related Art
Plasma display panels (PDP) can be classified according to the operation method into an AC type, in which the electrodes are covered with a dielectric and which is operated indirectly in the AC discharge condition, and a DC type, in which the electrodes are exposed to the discharge space and which is operated in the DC discharge condition. AC type plasma display panels can furthermore be classified according to drive method into a memory operation type, with which the memory of a display cell is used, and a refresh operation type, with which the memory of a display cell is not used. The luminance of a plasma display is proportional to the number of times of discharge. Since the luminance decreases as the display capacity increases in the case of said refresh type, this type is mainly used as plasma displays of low display capacity.
FIG. 1 is an exploded perspective view, which shows a display cell of a prior-art AC type plasma display panel. The display cell is provided with two insulating substrates 101 and 102 that are formed of glass. Insulating substrate 101 serves as the rear panel substrate and insulating substrate 102 serves as the front panel substrate.
Transparent electrodes 103 and 104 are provided at the side of insulating substrate 102 that opposes insulating substrate 101. Transparent electrodes 103 and 104 extend in the horizontal direction (transverse direction) of the panel. Also, bus electrodes 105 and 106 are disposed so as to overlap with transparent electrode 103 and common electrode 104, respectively. Each of bus electrodes 105 and 106 is a thin film electrode of approximately 1 to 4 xcexcm thickness comprising, for example, a CrCu thin film or Cr thin film and is provided to lessen the electrode resistance value between each electrode and an external drive device. A scanning electrode 115 is arranged from transparent electrode 103 and bus electrode 105, and a common electrode 116 is arranged from transparent electrode 104 and bus electrode 106. Furthermore a dielectric layer 112, which covers transparent electrodes 103 and 104, and a protective layer 114, which is formed of magnesium oxide, etc. and protects the dielectric layer 112 from discharge, are provided.
A data electrode 107, which is perpendicular to scanning electrode 103 and common electrode 104, is disposed at the side of insulating substrate 101 that opposes insulating substrate 102. Data electrode 107 thus extends in the vertical direction (longitudinal direction) of the panel. Barrier ribs 109, each of which extends in the longitudinal direction and partitions display cells that neighbor each other in the horizontal direction, are also provided. A dielectric layer 113, which covers data electrode 107, is provided, and on the side faces of barrier ribs 109 and the top surface of dielectric layer 113 is formed a fluorescent layer 111, which converts ultraviolet rays, which are generated by discharge of discharge gas, into visible light 110. A discharge gas space 108 is secured in the space between insulating substrates 101 and 102 by barrier ribs 109, and the interior of this discharge gas space 108 is filled with helium, neon, or xenon, etc. or a mixed gas of such gases.
Barrier ribs 109 are formed for example by layering a layer of frit glass on dielectric layer 113 and processing this layer to a predetermined shape by the sand blasting method.
With a plasma display panel that has been arranged thus, when the potential difference between scanning electrode 115 and common electrode 116 exceeds a predetermined value, discharge occurs and an emission 110 is thereby obtained.
Recently, plasma display panels that are finer are being required and the narrowing of the pitch of scanning electrode 103 and common electrode 104, which are the row electrodes, is deemed necessary. However, with a prior-art plasma display panel with the above-described arrangement, if just the pitch of the row electrodes is simply narrowed, erroneous discharge can occur due to interference of discharge among display cells that neighbor each other in the vertical direction and the image quality degrades accordingly in some cases.
Thus various plasma display panels have been proposed with which the rear panel substrate is provided with barrier ribs that take on a crisscross form and extend not only in the vertical direction but are also equipped with parts that extend in the horizontal direction and partition display cells that neighbor each other in the vertical direction (Japanese Unexamined Patent Publication No. 2001-93425, etc.).
If in the case where barrier ribs of crisscross form are employed, the height of the barrier ribs are made uniform, gas paths cannot be secured for the exhausting of the interior of the discharge space and the sealing of discharge gas in the discharge space, which are to be performed after adhering the front panel substrate and rear panel substrate together, and the manufacture process is thus made extremely difficult. Though it is possible for some amount of gas to flow since the surfaces of the barrier ribs and the surface of the protective layer are not perfectly flat, with just these conditions, the efficiency is extremely low and the productivity is significantly lowered.
Thus with the plasma display panel described in Japanese Unexamined Patent Publication No. 2001-93425, the height of the parts that extend in the longitudinal direction is made higher than the height of the parts that extend in the horizontal direction and the height of the intersections of these parts is made higher than the height of the parts that extend in the longitudinal direction.
With such a structure, gas paths for the exhausting and sealing processes can be secured and the efficiency is improved.
However, in manufacturing the plasma display panel described in Japanese Unexamined Patent Publication No. 2001-93425, the barrier rib parts that extend in the longitudinal direction must be formed after forming the parts that extend in the transverse direction. Thus in comparison to a prior arrangement provided with barrier walls comprising just parts that extend in the longitudinal direction, the number of processes is increased by the amount corresponding to the process of forming the barrier rib parts that extend in the transverse direction and the cost is thus increased.
Also, though barrier rib forming methods besides the sand blasting method include the printing method, etc., in the case where barrier ribs are to be provided with height differences, the number of processes will be increased correspondingly, no matter which method is employed.
Meanwhile, a plasma display panel, with which protruding parts are provided at regions of the dielectric layer of the front panel substrate that oppose the barrier ribs, has been disclosed for example in Japanese Unexamined Patent Publication No. Hei-8-250029, and by combining such a front panel substrate with barrier ribs of crisscross form of uniform height, gas paths may be secured while avoiding an increase in the number of processes for forming the barrier ribs.
However, since a process for forming protruding parts on the dielectric layer is newly required, increase of the overall number of processes cannot be avoided, and thus the productivity is lowered and the cost is increased in this case as well.
An object of the present invention is to provide a plasma display panel, which can be accommodated for increased fineness without lowering of productivity, and a manufacture method thereof.
A plasma display panel according to the present invention comprises a front panel substrate and a rear panel substrate that are disposed in opposing manner. Said rear panel substrate comprises an insulating substrate, barrier ribs, which are provided at the side of the insulating substrate that opposes said front panel substrate and which define display cells to block the transmission of discharge among neighboring display cells by said barrier ribs, first fluorescent layers, which are provided inside said display cells and convert the discharge generated inside the display cells into visible light, and second fluorescent layers, which are formed of the same materials as the first fluorescent layers and are selectively formed on said barrier ribs, thereby spaces are selectively formed between said barrier ribs and said front panel substrate.
Said second fluorescent layers may be formed on said barrier ribs, which are disposed between mutually neighboring display cells in which are formed the first fluorescent layers that convert the discharge to visible light of the same color with each other.
Also, said display cells may be arranged in matrix form, said barrier ribs may take on a crisscross form, first fluorescent layers that convert the discharge into visible light of the same color may be provided according to column in display cells that form a column in the direction perpendicular to the direction in which the scanning lines extend, and said second fluorescent layers may be formed on said barrier ribs disposed between all mutually neighboring display cells in at least one column of said display cells.
The thickness of said second fluorescent layer is preferably 5 to 15 xcexcm.
With the present invention, spaces of approximately the same thickness as the second fluorescent layers exist between the barrier ribs and the front panel substrate, and in the process of exhausting the gas inside discharge spaces after adhesion of the front panel substrate and the rear panel substrate and prior to the sealing in of discharge gas in the manufacturing process, said spaces are used as exhaust paths for making the gas inside the discharge spaces reach exhaust tubes readily and be exhausted to the exterior. Likewise in the process of sealing in discharge gas, said spaces are used as introduction paths for making the discharge gas reach the interiors of the respective discharge spaces readily. The lowering of the exhaust efficiency and the efficiency of sealing can thus be avoided even if each display cell is surrounded by barrier ribs. As a result, discharge gas can be made to exist appropriately in the discharge spaces without fail and excellent display characteristics can be obtained. Furthermore, since display cells that neighbor each other in the column direction are partitioned by the barrier ribs, erroneous discharge will not occur. The non-discharge gap can thus be narrowed and increased fineness can be accommodated for readily. Furthermore, since both the first and second fluorescent layers can be formed in the same process by screen printing, etc., cost increases due to increase in the number of processes can be avoided.
A plasma display manufacturing method according to the present invention comprises the steps of forming a front panel substrate, forming a rear panel substrate, and adhering said front panel substrate and rear panel substrate together. Said rear panel substrate is formed by the steps of forming, on an insulating substrate, barrier ribs, which partition display cells to block the transmission of discharge among neighboring display cells, and forming, respectively inside said display cells, first fluorescent layers, each of which converts the discharge generated in the corresponding display cell to visible light, and forming, selectively on said barrier ribs, second fluorescent layers, which are formed of the same materials as said first fluorescent layers.
Said first and second fluorescent layers may be formed by the step of forming said second fluorescent layers on said barrier ribs that are disposed between mutually neighboring display cells in which are formed first fluorescent layers that convert the discharge to visible light of the same color with each other.
Also, said display cells may be arranged in matrix form, said barrier ribs may take on a crisscross form. Said first and second fluorescent layers may be formed by the step of forming the first fluorescent layers, which convert the discharge into visible light of the same color, according to column in display cells that form a column in the direction perpendicular to the direction in which the scanning lines extend and forming said second fluorescent layers on said barrier ribs between all mutually neighboring display cells in at least one column of said display cells.